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The LM is a commonly used popular step-down switching regulator IC. The adjustable version can take in input voltage from 4. Note: The LM is of many types. The adjustable version LMADJ is the most commonly used and hence we will discuss only about that in this article.
The Complete Technical Details can be found at the datasheet given at the end of this page. The LM is known for its high current rating of 3A. It is available in many versions with fixed output voltage like 3. The IC is basically a buck converter that operates on KHz switching frequency, it takes in an input voltage and uses the internal switching circuit to regulated a desired output voltage. It has high efficiency and in-built Thermal shutdown and current limit functionalities.
So if you are looking for a small high package, easy to use high current buck converter IC then LM might me the right choice for you. The LM is very easy to use because it requires very minimum number of components. The unregulated voltage is given to pin 1 Vin across a filter capacitor to reduce input noise. If made high the IC will enter shutdown mode and prevent leakage current.
This feature will be useful to save input power when operating via battery. The feedback pin is the important pin which sets the output voltage. It sense the output voltage and based on the value of this output voltage the switching frequency of the internal switch is adjusted to provide the desired output voltage. Finally the output voltage is obtained through pin 2 through an LC filter. The complete circuit diagram is given below, you can often find these circuit in the LM DC Converter module.
The aboce circuit diagram shows the feedback pin getting the feedback voltage from a voltage divider circuit formed with Resistors R1 and R2. The value of this R1 and R2 decides the output voltage of the IC. The formula to calculate R1 and R2 is given below.
Here the value of Vref can be considered as 1. It is also possible to use a variable resistor in place of R1 to control the output voltage. This makes the IC easier to use in Variable power supply circuits. Subscribe to stay updated with industry's latest Electronics components and news. Component Datasheet. LM Regulator Datasheet. Tags Switching Voltage Regulator. Get Our Weekly Newsletter! Sets the output voltage using divider network using output voltage feedback.